Last night i got on the interstate and drove 40 miles at 80 mph. I had the ac on just vent not max and the blower on low. When i got off the interstate my pickup wouldn't idle. I had to keep it running. After alittle while with the ac off it slowly started to pick back up. Coming home i ran 80 again only no ac and it ran fine and idled fine when i got home. I watched the temp gauge so i know it didn't get hot. Any thoughts BTW 1998 ram 12 valve cummins 4x4 THANKS JARED

 

thats odd. . .I'm wondering if you have a vacuum kick down that got stuck. theres nothing electronic on that engine and I doubt the A/C would pull that much.